The present invention relates to livestock houses and more particularly to power ventilated livestock houses wherein the livestock have a low tolerance to excessive temperatures. More particularly the present invention relates to emergency ventilation of such livestock houses whereby normally closed ventilation openings may be automatically opened. In even greater particularity the present invention may be described as a thermally responsive actuator which opens the ventilator openings in the event of a power failure or excess temperatures.
U.S. Pat. No. 3,915,377 exemplifies the basic concept for automatically opening closures on ventilated livestock houses and describes in detail the conventional ventilation of such a house in columns 2 and 3. That patent discloses a device which has an auxiliary power supply, such as a battery, that powers a resistance heater in order to burn through a heat fusible cord which holds a mechanical closure mechanism in place, thereby releasing the closures. A time delay is provided by a bimetallic element to prevent inadvertent actuation of the device during brief power failure, which could potentially necessitate numerous replacements of the severed cord, and increase the probability of the severed cord causing a secondary ignition.
A later model of the same type apparatus utilizes a printed circuit board having an L-C time delay feature to prevent inadvertent openings of the closure. Although quite suitable initially, these PC board components are subject to breakage and environmental fluctuation and, as is well known, the L-C time delay tends to decay over a period of time, therefore the device may not always prevent inadvertent opening of the closures.
While the foregoing devices are suitable for their intended purpose they require a plurality of parts subject to fatigue or replacement and leave something to be desired in terms of efficiency, economy, and reliability.